Reaction Steps
rac-(4aR,11bS)-11b-ethyl-10-methyl-1,2,4,4a,5,6,7,11b-octahydrospiro[dibenzo[a,c][7]annulene-3,2′-[1,3]dioxolan]-9-amine (24, R2=Ethyl) (0.178 g, 0.563 mmol) was dissolved in DCM (4 mL) then potassium acetate (0.138 g, 1.408 mmol) and acetic anhydride (0.115 g, 1.126 mmol) were added. After about 10 min sat. aq. NaHCO3 (3 mL) was added and the mixture was diluted with DCM (15 mL). The layers were separated and the organic layer was dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified on silica gel (12 g) using a gradient of 0-50% EtOAc in DCM. Product fractions were combined and concentrated under reduced pressure to yield rac-N-((4aR,11bS)-11b-ethyl-10-methyl-1,2,4,4a,5,6,7,11b-octahydrospiro[dibenzo[a,c][7]annulene-3,2′-[1,3]dioxolan]-9-yl)acetamide (25, R2=Ethyl) (0.125 g, 62%); LC/MS, method 3, Rt=2.36 min, MS m/z 358 (M+H)+. 1H NMR (400 MHz, DMSO) δ 9.12 (s, 1H), 7.13 (s, 1H), 6.99 (s, 1H), 3.89-3.73 (m, 4H), 2.87-2.81 (m, 1H), 2.67-2.59 (m, 1H), 2.39-2.32 (m, 1H), 2.22-2.06 (m, 1H), 2.15 (s, 3H) 2.02 (s, 3H), 2.01-1.91 (m, 2H), 1.69-161 (m, 3H), 1.58-1.51 (m, 1H), 1.49-1.20 (m, 5H), 0.61 (t, J=7.5 Hz, 3H).
